Hydrogen is an important product for refinery and chemical use. Therefore, it has become more important to recover hydrogen from gas mixtures and waste gas streams. Conventional technology for the recovery of hydrogen from hydrocarbon mixtures is based on cryogenic fractionation. This is a well-developed, fully-matured technology based on the expenditure of energy for the generation of the low temperatures required for fractionation of hydrogen/light hydrocarbon mixtures. With increasing costs of energy, it is essential to develop purification methods which are potentially less energy intensive. Such techniques would entail the use of a separating agent along with reduced quantities of energy, or low-grade, inexpensive energy, as for example waste heat.
One potential purification method is by employing a hydrogen sorbent, such as the sorbent alloys disclosed in British Pat. No. 1,291,976. The sorbent in the British patent is an alloy of elements A and D where A is calcium or a rare earth metal and D is nickel or cobalt. These sorbents readily form hydrides under appropriate conditions. Recently, alloys of the type RM.sub.5 where R is a rare earth metal and M is a transition metal have been studied for their hydrogen absorption capacity. However, one of the basic problems with alloys of the type RM.sub.5 is their tendency to pulverize upon repeated hydrogenation/dehydrogenation procedures. The continuously diminishing size of the alloy particles makes the use of such systems in either a fluidized or fixed-bed process commercially unacceptable due to excessively high pressure drop across the reactor bed resulting from the crushed particles. Further, the handling of such powder size alloys is dangerous since the powder form can be pyrophoric and the small particles can become lodged in the lungs. A means has now been found to reduce the attrition of a particularly desirable hydrogen sorbent alloy.